Page 465 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

440 CHAPTER 2

VetBooks.ir trimester. The cause is unknown. The condition well as the option of a caesarean section. In a simple
torsion with no complications, the uterus is returned
is palpable per rectum/vagina. Treatment is with
smooth muscle relaxants, reduced feed intake
and regular walking exercise. to a normal position and the pregnancy is allowed to
continue to term. These pregnancies then constitute
high-risk pregnancies and require careful monitor-
Diagnosis ing thereafter. Correction at parturition usually
Rectal palpation is essential to confirm the diagnosis. results in immediate delivery of the foal, often with
The tension and position of the uterine broad liga- some judicious manual assistance.
ments vary in respect to the direction of the torsion,
but in either case a tight band (the stretched ligament) Prognosis
is palpated coursing diagonally across the abdomen. The prognosis depends on the degree of torsion and
In the more common clockwise (from behind) tor- when it occurs in the pregnancy, as well as the efficiency
sion, the left broad ligament courses across the dor- and timing of the correction that is required. In some
sal aspect of the uterus from left to right, and the studies, 50% of foals and 70% of mares survived after
right broad ligament disappears ventrally. The fetus surgical correction. The prognosis is better if the tor-
is usually displaced cranially. The amount of tor- sion occurs prior to 320 days. Complications involving
sion can vary from mild to severe (90–720°). The rupture of the uterus or vessel damage gravely worsen
greater the rotation, the more effect there will be on the prognosis for the mare and foal.
the uterine circulation, the placenta and the fetus.
Assessment of the fetus via transabdominal ultra- HYDROPS AMNION/ALLANTOIS
sound should also be performed if possible.
Vaginal examination, visually or digitally, is often Definition/overview
unhelpful because the cervix and cranial vagina are This is a sporadically occurring condition of late preg-
rarely involved (unlike in cattle). If the cervix is nancy in mares and is more common in multiparous
involved, it is not palpable or visible. mares. It involves an abnormality of the fetal mem-
branes (either amnion or allantois, or both together).
Management Fetal abnormalities commonly accompany this condi-
Early intervention is vital to prevent local hypoxia tion. Rapid accumulation of placental fluids leads to
and congestion, which may lead to fetal death or sudden-onset abdominal enlargement in the last tri-
even uterine rupture. Uterine torsion at parturition, mester of pregnancy. Normal placental fluid volumes
where the cervix is relaxed, the degree of torsion are allantois 8–15 litres and amnion 3–5 litres, and in
mild and the fetus palpable through the cervix, can hydroallantois cases volumes from 120–220 litres have
be corrected manually using rocking of the fetus. been reported. Circulatory problems, uterine rupture
Some clinicians advocate rolling under general and rupture of the abdominal wall can all occur sec-
anaesthesia using the ‘plank in the flank’ method, ondarily and severely affect the prognosis. Rectal pal-
but this can be unsuccessful and lead to serious pation and ultrasonography confirm the diagnosis and
complications such as premature separation of the the mare should be either induced or aborted.
placenta, uterine rupture or arterial damage. The
mare is rolled in the direction of the torsion and the Aetiology/pathophysiology
procedure may need to be repeated to achieve com- Hydrops allantois is the more common and is usu-
plete correction, which is confirmed by rectal palpa- ally due to placental abnormalities, which lead to
tion. In most cases, surgical correction is used, either excessive accumulation of fluid in the allantoic cav-
standing via a flank laparotomy (a two-sided approach ity with, or without, fetal abnormalities such as
is often required) or under general anaesthesia via wry neck, hydrocephalus and ventral herniation.
a ventral midline laparotomy. The latter technique Hydrops of the amniotic cavity is extremely rare and
has the advantage of allowing better visualisation of is due to placental abnormalities, either inflamma-
the uterus, ligaments, blood supply and GI tract and tory or vascular, and/or fetal abnormalities leading
identifying any damage and its subsequent repair, as to an inability of the fetus to swallow normally.